[PATCH 2/5] drm/i915: Wait for gen3 reset status to be asserted

[Chris Wilson]

After we assert the reset request (and wait for 20us), when the device
has been fully reset it asserts the reset-status bit. Before we stop
requesting the reset and allow the device to return to normal, we should
wait for the reset to be completed. (Similar to how we wait for the
device to return to normal after deasserting the reset request.)

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_uncore.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index 7af78043105f..478a8f44a782 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -1555,19 +1555,27 @@ static bool i915_reset_complete(struct pci_dev *pdev)
 	u8 gdrst;
 
 	pci_read_config_byte(pdev, I915_GDRST, &gdrst);
-	return (gdrst & GRDOM_RESET_STATUS) == 0;
+	return gdrst & GRDOM_RESET_STATUS;
 }
 
 static int i915_do_reset(struct drm_i915_private *dev_priv, unsigned engine_mask)
 {
 	struct pci_dev *pdev = dev_priv->drm.pdev;
+	int err;
 
 	/* assert reset for at least 20 usec */
 	pci_write_config_byte(pdev, I915_GDRST, GRDOM_RESET_ENABLE);
 	usleep_range(50, 200);
+
+	err = wait_for(i915_reset_complete(pdev), 500);
+
 	pci_write_config_byte(pdev, I915_GDRST, 0);
+	usleep_range(50, 200);
+
+	if (!err)
+		err = wait_for(!i915_reset_complete(pdev), 500);
 
-	return wait_for(i915_reset_complete(pdev), 500);
+	return err;
 }
 
 static bool g4x_reset_complete(struct pci_dev *pdev)
-- 
2.15.1